I Am Taking Birth Control Pills For More Than 10yrs

I am taking birth control pills for more than 10yrs already. My OBgyne advised me to stop taking the pills because I didn't have my period last August 2016. I had pregnancy test and yes it was negative. I had dark brown spotting on the following months instead of my period. Dec no spotting and no intercourse. Then jan 31,2017 came I had dark brown spotting again instead of my period. Is there anything serious that I need to know?